The Research On Chemo/Biosensors Based On Fe₃O₄/Self-reduced Graphene Nanomaterials

With the rapid development of nanotechnology, novel multifunctionalnanocomposites attracted wide attention due to its excellent performance. Iron oxide(Fe3O4) nanoparticle has become one of the most versatile magnetic nanomaterialsattributing to their large specific surface area, excellent catalytic and adsorptionability. As for graphene, its special structure and excellent performance make it thefocous in field of chemical and biological sensing since it was discovered. Synergisticeffect induced by the incorporation of nanoparticles and graphene leading to specialand excellent chemical and physical properties of the resulting nanocomposites, thus,metal oxide nanoparticles-graphene nanocomposites have potential applications in theareas of biological analysis and detection. In this thesis, the Fe3O4/reduced graphene(Fe3O4/rGO) nanocomposites were one-pot synthesized, and benefited from the highconductivity, catalytic activity and adsorptive ability, biosensors based on Fe3O4/rGOnanocomposites have been developed. The main contents are summarized as follows:1. A novel, sensitive, nonenzymatic electrochemical sensor for the reliabledetection of extracellular H2O2released from living cells was fabricated based on theFe3O4/reduced graphene oxide (Fe3O4/rGO). GO was directly reduced by Fe2+, leadingto Fe3O4NPs in situ deposited onto self-reduced GO sheets, so that to simply andefficiently synthesize Fe3O4/rGO nanocomposites. Morphologies and crystalstructures of the Fe3O4/rGO nanocomposites were observed. Electrochemicalperformances of the Fe3O4/rGO nanocomposites modified glassy carbon electrode(GCE) were studied by cyclic voltammetry and amperometry. The resultsdemonstrated that this modified electrode exhibited excellent electrocatalyticperformance towards the reduction of H2O2at a potential of0.3V with a highsensitivity of387.6A mM1cm2and a detection limit as low as0.17M (S/N=3).Moreover, good anti-interference property, reproducibility, and long-term stability ofthe enzymeless sensor were achieved. Due to these remarkable analytical advantages,a novel, effective approach for detection of H2O2released from HeLa cells stimulatedby CdTe quantum dots (QDs) was established by the constructed sensor.2. Based on the intrinsic enzyme mimetic activity of Fe3O4magneticnanoparticles, the Fe3O4/rGO nanocomposites was used in colorimetric analysis ofcancer cells. The Fe3O4/rGO nanocomposites could catalyze the oxidation of the substrate2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate)(ABTS) in the presenceof H2O2to produce a green color. The Fe3O4/rGO composites could bind to the cellssurface by electrostatic interaction, and the more Fe3O4/rGO composites bind onto thecells surface and the longer binding time, the more green the solution color are getting.The Fe3O4/rGO nanocomposites were then applied to cells-based colorimetric analysisby observing the difference in the color of the solution due to the different amount ofFe3O4/rGO composite binding onto the cells surface, and the color change could beobserved by naked eye.3. An electrochemical sensor for sensitive and simultaneous detection of guanineand adenine was constructed. Based on the extraordinarily performance of Fe3O4/rGOnanocomposites, the Fe3O4/rGO modified electrode exhibited remarkableelectrocatalytic activity towards the individual and simultaneous oxidation of guanineand adenine. The modified electrode possessed high sensitivity, wide linear range andlow detection limit for the electrochemical determination of guanine and adenine.Good anti-interference property, reproducibility, and stability were also achieved.This modified electrode was further used for the simultaneous determination ofguanine and adenine or the content in acid-denatured calf thymus DNA withsatisfactory results.